We had this one system start to show very odd behavior yesterday. We had multiple drive failures and some self inflicted injury that caused our inode table to get out of sync for some of our hardlinked directories. We use the awesomeness of rsnapshot to take snaps of some of our filesystems onto large 100T+ filesystems with xfs a bit like this one:

The filesystem was not all that poorly and stage 7 fixed the missing inode meta data swiftly, these were all hardlinks that had a simple reference count problem you can see below. The filesystem was showing an interesting feature though, "rm -rf directory" would give "directory not empty":